Preparation and in-vitro release of metformin hydrochloride sustained-release pellets

Objective: To prepare metformin hydrochloride(MH) sustained-release pellets,and to investigate their in-vitro release behavior and the release mechanism.Methods: MH pellets were prepared by a centrifugal granulation method.Ethyl cellulose aqueous dispersion(Surelease) and acrylic polymers aqueous dispersion(Eudragit NE30D,RS30D) were used as sustained-release coating materials with fluid bed.The effects of different coating materials,coating weight,curing time and release medium on the in-vitro release were determined.Results: MH pellets prepared by the centrifugal granulation method had good roundness,and were suitable for coating.Coating weight of 11% Surelease had satisfactory sustained-release behavior within 12h,and the drug release amount could reach over 85%.The pellets showed similar release behaviors in different release media including water,0.1mol·L-1 HCl and PBS 6.8,and their release model was zero-order due to the release mechanism of diffusion through the non-porous membrane.Conclusion: MH sustained-release pellets prepared by the centrifugal granulation method and coated by Surelease possesses an obvious sustained-release property in 12h and their release model is zero-order.